Computerized Facade Allows Skyscraper to Inhale and Exhale

It's hard being green in a high rise, and if you want operable windows, forget it. You might as well turn the place into a coal plant. But German architects Sauerbruch Hutton have figured out a way to let in fresh air without tossing their eco cred. The secret: a high-tech skin.

As Peter Fairley at IEEE Spectrum reports, the firm's KfW Bankengruppe office building, in Frankfurt, has the world's first "pressure ring" facade. That's a fancy way of saying that it balances pressure throughout the building, allowing occupants to crack windows without turning their offices into a set from Twister. (Typically in a high rise building with operable windows, you get pressure differentials that generate huge cross breezes.)

In the KfW tower, sensor-controlled ventilators on the outer skin (see detail below) open and close throughout the day in response to temperature, wind direction and speed, among other factors, throwing a ring of positive pressure around the building. That air is drawn into offices through floor vents and windows along an inner facade workers control; then, it's exhausted into the building core. So what you get is a system of natural ventilation that eliminates the need for AC and heat in the fall and spring. And in extreme weather, when you need an artificial bump, the pressure balance won't throw your heating and cooling systems out of whack.

The facade's expected to help the building consume just a third as much energy as a typical American office building.

Plus, it's great-looking. The serrated skin makes the building pop — literally — and all those splashy colors do wonders for Frankfurt's perennially gray sky.